Print out and start the process of having your students revise their work. Students can attach as many copies of this as needed to their original assessment - either to earn points back, before they complete a retake, or simply as part of the learning process. In addition to having students re-work problems they missed, help them to become more self-aware by having them determine the type of mistake (i.e. didn't know how to do it, careless error, calculator mistake, or something else). This part